This invention relates to easy open metal container end closures or closure members and particularly to those provided with preformed tabs that can be pushed in manually to gain access to the contents of the container to which an end closure is attached. Upon being pushed in, the instant tabs do not become readily separated from their associated end closures to become lost and thereby further contribute to the litter problem as is the case with conventional pull ring tear tabs.
At the present time, the most commonly used easy open devices for metal container closures attached to beverage cans and the like comprise metal pull rings or pull tear tabs. These rings or tabs become readily separated from their respective container closures upon opening and unless deposited in a refuse can are frequently dropped upon the ground or overboard from a boat, to form litter as well as possible hazards to marine life, or to people walking barefoot in the areas where the tabs fall upon the ground.
Not only have the separable metal pull rings or tabs created significant litter problems to the point, whereby at least one state has prohibited the use of containers provided with such rings within the state, they also involve a substantial number of precise manufacturing steps or procedures and extra metal. Since the pull ring is normally attached to a rivet formed integrally with the closure member, care must be exercised in attaching the ring to the rivet to prevent the rivet from being destroyed or weakened whereby the closure member will not pass quality control inspection during manufacture.
Attempts have been made in the past to overcome the various problems presented by the pull ring type easy open closure members by avoiding the use of such separable pull rings in favor of push button type tabs formed integrally with the closure member proper. Examples of such push button tabs for closure members are shown in U.S. Pat. Nos. 2,120,186, 2,187,433, 2,261,117, 3,362,569, 3,246,791, 3,355,058, 3,779,417, 3,760,752, 3,759,206 and Design Pat. No. 226,171, Page 9 of the "Wall Street Journal" for May 23, 1973, and the Federal Republic of Germany published (Offenlegungsschrift) Pat. application No. 2,341,077 of Apr. 18, 1974. In the easy open container closures of the last two issued United States patents, the push button opening tab is adapted during manufacture to be first completely fractured or severed from the container closure proper except for a small hinge and then pushed back into place and sealed to the container closure proper by means of an appropriate plastic sealant. These plastic sealed closure tabs, however, are difficult to make leakproof and sanitary on a mass production basis and, in any event, are still relatively expensive to produce because of the number of complex manufacturing steps and tooling involved plus the sealant materials required.